Shredded serpentine belt...again

So....mechanic came and reported everything fine w respect to pulleys. Upon further inspection I did find several rough spots on crankshaft pulley which most likely over time shredded the belt. Wire brushed crankshaft in addition to all pulleys whilst dipping wire brush in acetone to remove residue from shredded belt in pulley gooves. Reinstalled new quicksilver belt and tensioned as close to other (port) engine belt. Powered up the engine and gradually increased rpms to approx 2800 with no issues. Temp remained just below 170. Took her out for sea trial and once I throttled her up, she sounded as if she was slipping and rpms lagged that of the other engine. Imortant to note that in addition to feeling a slip in the belt, I noticed a rumble/vibration while attempting to throttle up. Good news is she did not overheat. Took her back and upon inspection, the belt seemed a bit less taught than the other engine. Retensioned the belt to match that of the port engine and decided to wait til tomorrow as wife was aboard you may know the rest.

Question.. is it possible the loosely tensioned belt would cause the "spinning" and "rumble/vibration"? Thx in advance.
 
sorry if you already know this, but there is a 'method' to adjusting the tension on the belt.....it been a little while since i adjusted a belt tension but IIRC you have to loosen the larger nut on the idler pulley then use the small nut on the pulley to adjust the belt tension....when you have the belt tension you want then tighten the larger nut to lock the pulley into position.....if you have the owners manual the process may be in there....if not a simple Google search should find it....

cliff
 
rumble/vibration is not good. You want to figure where that's coming from. Not sure how you would feel the belt sipping. You want to paint those pulleys after you clean them up , so the rust doesn't return
 
I am still betting on the bearings being shot in one of the two pumps on that engine. If the pulleys are spinning that doesn't mean they are not shot. Is there any "wobble" or play in either pump pulley when there is no belt on them? They should not have any noticeable play. What about any other pulleys on that belt, including the tensioner pulley.
 
CliffA said:
sorry if you already know this, but there is a 'method' to adjusting the tension on the belt.....it been a little while since i adjusted a belt tension but IIRC you have to loosen the larger nut on the idler pulley then use the small nut on the pulley to adjust the belt tension....when you have the belt tension you want then tighten the larger nut to lock the pulley into position.....if you have the owners manual the process may be in there....if not a simple Google search should find it....

cliff
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Thank you. Yes, exactly my procedure.
 
scoflaw said:
rumble/vibration is not good. You want to figure where that's coming from. Not sure how you would feel the belt sipping. You want to paint those pulleys after you clean them up , so the rust doesn't return
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Scoflaw, hmm..good question..not sure how to answer how I felt it slip...maybe more audible than feel. And yes, I will definitely paint the pulleys. Rustoleum a good choice? Agreed that rumble vibration is not good. Weather has been crap here today. Will go sea trial her after having retensioned/tightened the belt.

Creekwood..zero play in all pulleys without belt installed. As an aside and to restate from the original post, as a result of the belt shredding, I did overheat but engine was shut down immediatley and was not even close to approaching 2000 rpms. All fluids have been checked and oil and coolant have zero indication of any intrusion from one to the other. After reading up on several other sites, I must admit, I did not recheck the tension after running the boat in neutral while increasing rpms gradually to approx 2500 after initial install and belt was not tensioned as it had been prior to leaving the dock. No mechanic here, but hoping the improper/lose tension was the culprit. Will report back tomorrow after mother nature gets the sand out of her shorts. Thx much for your input. Greatly appreciated.
 
you will not 'feel' anything when a belt slips....you may 'hear' a squealing or chirping sound.....

I think you are chasing two different things that are not related....there is no connection between a slipping belt and the engine running rough.....in fact an engine will run just fine without the belt installed....for a short while until it starts to overheat....the good news is I don't think you blew a head gasket on the engine when it ran hot since the engine did not overheat when you ran it after the new belt was installed....it may be something as simple as a spark plug wire pulled loose from the spark plug.....if the engine has not had a tune-up in a while you may want to start there...in MANY cases a tune-up cures an issue with the engine running poorly.....

good luck...

cliff
 
CliffA said:
you will not 'feel' anything when a belt slips....you may 'hear' a squealing or chirping sound.....

I think you are chasing two different things that are not related....there is no connection between a slipping belt and the engine running rough.....in fact an engine will run just fine without the belt installed....for a short while until it starts to overheat....the good news is I don't think you blew a head gasket on the engine when it ran hot since the engine did not overheat when you ran it after the new belt was installed....it may be something as simple as a spark plug wire pulled loose from the spark plug.....if the engine has not had a tune-up in a while you may want to start there...in MANY cases a tune-up cures an issue with the engine running poorly.....

good luck...

cliff
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Thx CliffA. In hindsight, I may have miscategorized the discription as "engine" when in reality I really don't know what the rumble came from. One extra ingredient would be the synchronizer gauge for the engines showed a much weaker reading for this engine while both were throttled equally. At idle all is fine...only under load did this occur. I will tend to checking the plugs this afternoon. Thx much.
 
if the throttles for both engines are in about the same position and one engine is lacking in rpm there is a VERY good chance that engine indeed has a running issue....I had that recently on my boat when a fuel injector went bad on my starboard engine.....both engines would idle fine and rev fairly evenly until around 3,500 rpms....then the port engine would continue to rev all the way to WOT which is around 5,000 rpm's but the starboard engine would not rev past 3,800 rpm's even with the throttle pushed all the way open....

cliff
 
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CliffA said:
if the throttles for both engines are in about the same position and one engine is lacking in rpm there is a VERY good chance that engine indeed has a running issue....I had that recently on my boat when a fuel injector went bad on my starboard engine.....both engines would idle fine and rev fairly evenly until around 3,500 rpms....then the port engine would continue to rev all the way to WOT which is around 5,000 rpm's but the starboard engine would not rev past 3,800 rpm's even with the throttle pushed all the way open....

cliff
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Any possibility that an over heat due to shredded belt could cause this? Or possibly just a coincidence?
 
if an engine is significantly over heated the result is usually a blown head gasket with maybe a warped head and it is possible the engine being ruined if water/coolant is allowed to enter the combustion chamber...since your engine seems to run fine (no obvious signs of running rough and no overheating and no steam from the exhaust) now after the new belt was installed and there are no signs of water/coolant mixed with the engine oil I doubt you have a blown head gasket...I am thinking the two things are not related unless someone accidentally pulled a spark plug wire loose or a ignition coil wire loose while working on the belt.....

cliff
 
CliffA said:
if an engine is significantly over heated the result is usually a blown head gasket with maybe a warped head and it is possible the engine being ruined if water/coolant is allowed to enter the combustion chamber...since your engine seems to run fine (no obvious signs of running rough and no overheating and no steam from the exhaust) now after the new belt was installed and there are no signs of water/coolant mixed with the engine oil I doubt you have a blown head gasket...I am thinking the two things are not related unless someone accidentally pulled a spark plug wire loose or a ignition coil wire loose while working on the belt.....

cliff
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Will definitely check this afternoon. Thx.
 
Creekwood said:
I am still betting on the bearings being shot in one of the two pumps on that engine. If the pulleys are spinning that doesn't mean they are not shot. Is there any "wobble" or play in either pump pulley when there is no belt on them? They should not have any noticeable play. What about any other pulleys on that belt, including the tensioner pulley.
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Creekwood...you may just have entered the bonus round. Finally down to the boat yesterday to retension belt and upon start up and increasing rpms, I now hear what I believe to be bad bearing noise. Not sure which pump but if this means anything, the raw water exhaust elbow on the port side of this engine (starboard) is much hotter than that of the starboard. Mechanic to check both pumps today.

As I'm not a mechanic, could you try to school me on why this would cause the issue which presented itself initially (no ability to throttle this engine up while engaged w tranny) Thanks.
 
you might want to purchase a 'mechanic's stethoscope' like this.....you can find them at auto parts stores for around $10-15.....it is very effective for identifying engine components that are making sounds they should not be making.....

shopping
 
msballin said:
Creekwood...you may just have entered the bonus round. Finally down to the boat yesterday to retension belt and upon start up and increasing rpms, I now hear what I believe to be bad bearing noise. Not sure which pump but if this means anything, the raw water exhaust elbow on the port side of this engine (starboard) is much hotter than that of the starboard. Mechanic to check both pumps today.

As I'm not a mechanic, could you try to school me on why this would cause the issue which presented itself initially (no ability to throttle this engine up while engaged w tranny) Thanks.
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Actually, no ability ...without vibration/rumble from wherever...to throttle...
 
CliffA said:
you might want to purchase a 'mechanic's stethoscope' like this.....you can find them at auto parts stores for around $10-15.....it is very effective for identifying engine components that are making sounds they should not be making.....

shopping
Click to expand...
CliffA...very cool. Never heard of. Thx!
 
msballin said:
Creekwood...you may just have entered the bonus round. Finally down to the boat yesterday to retension belt and upon start up and increasing rpms, I now hear what I believe to be bad bearing noise. Not sure which pump but if this means anything, the raw water exhaust elbow on the port side of this engine (starboard) is much hotter than that of the starboard. Mechanic to check both pumps today.

As I'm not a mechanic, could you try to school me on why this would cause the issue which presented itself initially (no ability to throttle this engine up while engaged w tranny) Thanks.
Click to expand...

Maybe an overheat issue. If the engine overheats the oil thins out and may cause the hydraulic valve lifters to collapse (not fully opening the valves). It causes a "bogging" feeling and the engine can't rev properly. Once it cools it works again. That happened on my prior boat when the mechanic used too thin a grade of oil on an oil change. Mine wasn't an overheat per se, (but was too hot for that viscosity of oil) but gave similar symptoms.
 
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I realize I am late to this story.....do you have a photo of the old (shredded) belt? Depending on where it is worn ....it will generally provide a clue as to the culprit. I understand your guy has checked the pulleys but those belts don't shred unless they are very loose or one of the pulleys is locking up or developing a high resistance.

In regard to the performance issue....as other have said that is probably unrelated.
 
Don,t over tighten. I had a slightly bent raw water pump bracket and it kept shredding the belts on my other boat. You can see that bracket move when tightening the belt.
 
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